Film gate



mar'chzz, 1938.

1 F. E. RUNGE 2,111,741

FILM GATE Filed Dec. 51, 1936 (H) I a 1;? 2

| E I i I l E I E E l I E l a I I J VJ 3nventor (Itto meg Patented Mar. 22, 1938 UNITED STATES FILM GATE Frank E. Runge, aklyn, N. J., assignor to Radio Corporation of America, a. corporation of Delaware Application December 31, 1936, Serial No. 118,518

This invention relates to a new and useful improvement in film gates, and more-particularly to the type of film gate used at the picture aperture of sound picture projectors.

; In projectors using film having a sound record thereon, the sound record is ordinarily located adjacent to one edge of the film, and it is necessary to prevent dam: ;e to the record as it passes I through the motion picture machine, in order to prevent the production of undesirable noises in the soundfreproducer.

In 16 mm. projectors it is customary to have sprocket-holes at one edge of the film only, and

to have the sound track located in the area corresponding tothe usual area of sprocket holes in silent picture film, at the opposite edge oi the him.

In using this type of film, it is sometimes difilcult to maintain the film perfectly flat at the picture gate, as theavailable contact area ad-f jacent the sound track is quite small. he pres-= ent invention pertains more particularly to gate for accomplishing this purpose.

In a film gate constructed in accordance with my invention the pressure shoe is provided with film contacting portions of unequal surface areas at the two sides of the film. Springs are pro,- vided to hold the pressure shoe in contact the film, and these springs are so located in re= lation to the film contacting surfaces as to give a uniform pressure per unit area on each of surfaces. These same springs also serve to maintain the pressure shoe in place on the gate and are enclosed within tubular members which serve I as guides for the pressure shoe in its movement and also serve to latch the pressure shoe in oper= ativeposition.

One object of the invention is to provide a film gate which is readily removable for cleaning.

Another object of the invention is to provide 0 a film gate through which film may be readily threaded.

Another object of the invention is to provide a film gate which will maintain the film flat at the picture projection point. 4 5 Another object of the invention is to provide a film gate which will have uniform wear at both edges of the pressure shoe, thereby greatly length ening the useful life of the shoe.

Other and incidental objects of the invention 50 will be apparent to those skilled in the art upon a reading of the following specification and an inspection of. the accompanying drawing, in which:

",Flgure'l is a side view or my improved film" 66 r t I 5 ll Clainn. (Cl. 88-17) Fig. '2 is a view of the pressure shoe, looking from the side toward the film;

Fig. 3 is a vertical section through the'pressure shoe on the line 3-3 of Fig. 2;

Fig. 4 is an elevation from the right hand side 5 of Fig. 3 and Fig. 5 is a section on the line 5-5 of Fig. 2.

Referring now to the drawing: The projector is provided with the usual center plate or housing l, upon which are mounted a base 2 for the 10 lens and film gate assembly, and an appropriate plate 3 through which light passes to the picture aperture. The base 2 carries a lens mounting barrel i, in which a projection lens 5 is fitted in proper focal relation to the film 6 15 On the rear of the barrel 4 is vmounted a bracket '1'! which supports the pressure shoe B of the film gate. If so desired the barrel 4 and the bracket l! may be made movable as a unit in any of the usual ways in which one element of 20 a film gate may moved, as, for example, the unit may be hinged at the bottom to swing outwardly, it may be mounted on a parallel-link motion, or it may be mounted on one or more slides permitting it to'slide longitudinally This. 25 however, is not essential, as the gate portion 8 may be moved in relation to the bracket l a sufficient distance to permit threading of the The stationary portion 9 of the film gate is se- 30 cured to the base 2 by means of screws it and ii, so that it may be readily replaced in case of excessive wear. This stationary member 9 may be either smooth on its film contacting face, or it may be appropriately relieved beneath the sound 35 track and picture portions in the same manner as the pressure shoe 8, as shown in Fig; 2.

The bracket 11' is provided with two extending legs having L-shaped slots l2 and i3 which cooperate with the extending tubular members it and [5 of the pressure shoe 8 which is relieved beneath the sound track and picture portions. so as to provide aface l6 which cooperates with the him at the sprocket hole, and a. second narrower face ll! which coacts with the face of the film between the pictures and the sound track.

It will be apparent that ii pressure were uniiormly applied to the pressure shoe, the pressure on the portion i'i would be much greater per unit area than on the portion l6, and this nar- 5o rower portion li would therefore wear much more rapidly. Furthermore, either the pressure on the face ll would be so great as to damage the film, or the pressure on the portion I6 would be inadequate to maintain the sprocket hole edge film.

As shown in Fig. 3, the tubular members I4 and I! are each provided with a compression spring II which coacts with a follower l9, movable within the tube, and which is stopped by a pin 20. The top and bottom of the members II and I5 are each provided with an appropriate slot 2| which may pass over the flat ends of the bracket 1.

In placing the pressure shoe I in operative position, the followers iii are placed against the legs of the bracket 1, and the shoe is then pressed toward the lens 5, compressing the springs until the pins 20 drop into the slots l2 and It. When the gate is released. the spring ill moves the pressure shoe 0 toward the iixed member 9, causing the pins 20 to move into the bottom portions of the L-shaped slots, and thereby preventing vertical displacement of the pressure shoe 8, while at the same time permitting the pressure shoe to move horizontally in accordance with any irregularity in the film, such as splices or the like.

Asshown in Fig. 1, and in greater detail in Fig. 5, the pressure shoe 0 is provided with an appropriate picture aperture 22, through which light transmitted by the film 6 may pass to the objective 5.

It will be apparent from the foregoing that I have provided a readily removable film gate in which the pressure shoe may be readily removed for cleaning or repair, and which provides a uniform pressure per'unit area on all portions of the film in contact with the shoe.

Having now described my invention, I claim:

A pressure shoe for a film gate including a tubular spring retaining member, a compression spring therein, a retaining plunger in cooperative relation with said spring, and a pin extending across said tubular member, the said tubular member being slotted whereby the said member, the said stop, and the said plunger may coact with a correspondingly slotted bracket for removably retaining the said pressure shoe in operative position. FRANK E. RUNGE. 

